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-rw-r--r--mysys/mf_radix.c60
1 files changed, 60 insertions, 0 deletions
diff --git a/mysys/mf_radix.c b/mysys/mf_radix.c
new file mode 100644
index 00000000..8f044cf9
--- /dev/null
+++ b/mysys/mf_radix.c
@@ -0,0 +1,60 @@
+/* Copyright (c) 2000, 2007 MySQL AB
+ Use is subject to license terms
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; version 2 of the License.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
+
+/*
+ Radixsort for pointers to fixed length strings.
+ A very quick sort for not to long (< 20 char) strings.
+ Neads a extra buffers of number_of_elements pointers but is
+ 2-3 times faster than quicksort
+*/
+
+#include "mysys_priv.h"
+#include <m_string.h>
+
+ /* Radixsort */
+
+my_bool radixsort_is_appliccable(uint n_items, size_t size_of_element)
+{
+ return size_of_element <= 20 && n_items >= 1000 && n_items < 100000;
+}
+
+void radixsort_for_str_ptr(uchar **base, uint number_of_elements, size_t size_of_element, uchar **buffer)
+{
+ uchar **end,**ptr,**buffer_ptr;
+ uint32 *count_ptr,*count_end,count[256];
+ int pass;
+
+ end=base+number_of_elements; count_end=count+256;
+ for (pass=(int) size_of_element-1 ; pass >= 0 ; pass--)
+ {
+ bzero((uchar*) count,sizeof(uint32)*256);
+ for (ptr= base ; ptr < end ; ptr++)
+ count[ptr[0][pass]]++;
+ if (count[0] == number_of_elements)
+ goto next;
+ for (count_ptr=count+1 ; count_ptr < count_end ; count_ptr++)
+ {
+ if (*count_ptr == number_of_elements)
+ goto next;
+ (*count_ptr)+= *(count_ptr-1);
+ }
+ for (ptr= end ; ptr-- != base ;)
+ buffer[--count[ptr[0][pass]]]= *ptr;
+ for (ptr=base, buffer_ptr=buffer ; ptr < end ;)
+ (*ptr++) = *buffer_ptr++;
+ next:;
+ }
+}